Twist drill-bit sharpening unit



Aug. 26, 1958 G. T. ROSHOLT TWIST DRILL-BIT SHARPENING UNIT Filed Feb. 23, 1955 60/?000 Z AQS/IOLT .51 I d 7 dm yfl x vmyy 2,848,852 Patented Aug. 26, 1958 Unied TWIST DRILL-BIT SHARPENING UNIT Gordon '1. Rosholt, Minneapolis, Minn.

Application February 23, 1955, Serial N 0. 489,831

2 Claims. (Cl. 51219) This invention relates to twist drills. More particularly, it relates to a simplified and portable twist drill-bit grinding unit.

Many elaborate and complicated machines and assemblies have been designed for sharpening twist drillbits. The cost of such machines is such as to make prohibitive the ownership of the same by the home owner who utilizes a twist-drill only occasionally. Moreover, these costly assemblies are generally quite heavy and hence not readily portable. Also, they generally do not include a grinding wheel but require the previous existence of a motorized grinder of pedestal or bench type. This includes a separate source of rotary power to drive the grinding unit. My invention is directed toward making it financially feasible for every owner of an electric hand drill to have his own twist drill-bit grinding attachment which will obviate any need for the bigger and much more costly machines heretofore required.

It is a general object of my invention to provide a novel and substantially simplified attachment for an electric drill which will enable the user to sharpen his own drill bits quickly, efiiciently and inexpensively, using the electric drill itself for power.

A more specific object is to provide a novel and simple attachment for an electric drill which will enable the user to substitute the attachment for the drill bit in his drill and quickly, easily and efiiciently sharpen the drill bit therewith.

Another object is to provide a simple and inexpensive twist drill-bit grinding assembly which can be easily secured within a vise and utilized in combination with the electric drill to sharpen the drill bit.

Another object is to provide a highly simplified twist drill-bit grinder which requires a minimum of material and labor to manufacture and hence is very inexpensive and simple to operate.

These and other objects and advantages of my invention will more fully appear from the following description made in connection with the accompanying drawings, wherein like reference characters refer to the same or similar parts throughout the several views, and in which:

Fig. 1 is a front elevational view of one embodiment of my invention;

Fig. 2 is a plan view of the same;

Fig. 3 is an end elevational view of the same with part of the grinding wheel broken away;

Fig. 4 is a plan view of a second embodiment of my invention with parts thereof cut away; and

Fig. 5 is an end elevational view of the embodiment shown in Fig. 4 with parts thereof broken away.

As shown in Figs. 13, one embodiment of my invention may include a rigid upright plate member 6, the upper end of which is bent forwardly to form a sleevelike hearing 7. Extending forwardly from one edge of the plate 6 is another plate 8 which extends vertically also to form a rigid frame work therewith. The upper portion of the plate 8 is bent over into a horizontal position to form a platform 9, which is secured to the upright plate 6 by an overlapping portion 10. Extending outwardly from the rear edge of the plate member 8 is a mounting bracket 11 which is preferably formed integral with the plate member 8. This mounting bracket 11 extends at an acute angle to the vertical plate 8,v as best shown in Fig. 2. The upper edge of the mounting bracket is bent rearwardly into a horizontal abutment flange 12, and the free side edge of the bracket is also bent rearwardly into an abutment flange 13. These abutment flanges are spaced fromeach other, as best shown in Fig. 3, to permit the drill-bit receiving and guiding member indicated generally as M to pivot within an arc of approximately 50 degrees.

Mounted within the sleeve 7 is a shaft 14 whichextends through the sleeve and has outer end portions extending outwardly at opposite sides of the plate member 6, one end portion 15 is adapted to be received within the chuck 16 of an electric drill 17 which, as shown, is entirely supported by the shaft. This shaft 14 is held in place in the sleeve 7 by a spring-retaining plate 18, which fits into a groove in the shaft 15 provided therefor. At the opposite end of the plate- 6 a second retaining plate 19 fits into a secondv groove provided therefor in the shaft 14 so that the shaft is maintained in its proper position within the sleeve 7. The other end portion 20 of the shaft 14 has a grinding wheel 21 mounted thereon. This grinding wheel 21 is flanked by a pair of washers-22 and 23, and is secured to the shaft 15 for rotation therewith by a nut 24, which is threaded on the externally threaded end portion 20.

Pivotally mounted on the mounting bracket 11 is the drill-bit receiving and guiding member M. As best shown in Fig. 1, this member M is mounted on the bracket 11 outwardly of the grinding wheel 21 and the axis of pivot extends at an angle to the grinding surface of the wheel of about 15 degrees, as best shown in Fig. 2. The guiding member M is comprised of an elongated channel member 25 and it is supported by a pair of spaced straps 26 and 27 which join with a perforated plate 28. The perforated plate 28 is pivotally secured to the bracket 11 by a tubular-like rivet 29 which is swedged outwardly at its opposite ends rearwardly of the plate 23 and forwardly of the bracket 11, thereby permitting free, pivotal movement of the guiding member M about the axis which extends at an angle of 15 degrees to the grinding surface. The channel member 25 has a shallow groove or channel which faces away from the shaft 14 which carries the grinding wheel 21. Its depth is preferably between 6 and A; of an inch to permit the thumb of the user when grasping a small drill-bit of approximately A of an inch to extend sufiiciently far into the groove to insure a secure grip on the small drill-bit.

Mounted on the top of the platform 9 is an upstanding pivot post 34 which has a ball 31 at its top. An upstanding pivot bracket 32 is mounted on the ball 31 and is secured thereto by a pair of spaced perforated lower end portions 33 and 34-. At the upper end of the bracket 32 there is a pair of spaced upper end portions 35 and 36 which hold therebetween a ball-like member 37 which carries a magnifying glass 33. Thus universal movement is provided at both ends of the pivot bracket 32 to permit the magnifying glass 33 to be moved to any desired position. This glass is used to magnify the cutting end of the drill-bit 39 as it is applied to the side of the grinding wheel so as to enable the cutting edge to be presented properly to the side of the wheel 21. It will be noted that the channel member 25 is disposed on the opposite side of the drill-bit 3 relative to the point of pivot of said member which is at the tubular rivet 2 9.

Formed in the forward edge of the platform 9. is a plurality of notches 46, the bottom walls of which are shaped to conform to the cutting end of a properly ground twist drill-bit having a diameter of the width of the notch. These bottom walls are indicated by the.

numeral 41.

The embodiment shown in Figs. 4 and 5 includes a drill 45' carrying the rotatable shaft 46 which carries the grinding wheel 47. The grinding wheel 47 is secured bracket is free to pivot around the shaft 46 and its end portion is curved into a sleeve to encircle the shaft to accomplish the pivotal mounting thereon.

The mounting bracket 51 extends forwardly as shown inFig. 4 and carries at its forward end a drill-bit receiving and guiding member 52. This drill-bit receiving and guiding member 52 is constructed in the same manner as the drill-bit receiving and guiding member M described hereinabove, and it is pivotally mounted on the mounting arm 51 in the same manner as the member M is pivotally mounted on the plate 11. t is arranged and constructed so that the drill-bit which it receives will be presented at the proper angle to grind thesame just as in the case of the drill-bit receiving and guiding mem ber M.

When it is desired to utilize the embodiment shown in Figs. 1-3, the plate member 6 is fixedly secured within a vise V so as to support the same rigidly. The drill 17 is then secured to the shaft 15 by securing the chuck 16 on the free end thereof. The electric drill 17 may then be permitted to be supported solely by the shaft 15 as shown in Fig. l and the weight of the drill 17. will be more than ample to prevent rotation thereof so that when the drill is energized the shaft 15 will be rotated rapidly. In this manner the grinding wheel 21 is driven and both hands of the operator may be utilized to accomplish the drill-bit grinding operation. The magnifying glass is then swung into the position shown in Figs. 1 and 2 and the drill-bit 39 is inserted into the channel of the channel member 25 and moved lengthwise inwardly toward the rotating grinding wheel 21 until its cutting edge is about to register with the grinding surface thereof. V

The drill-bit 39 is gripped with the operatorsthurnb bearing against it and with the forefinger around the.

channel member 25 as clearly shown in Fig. 2. The cutting edge is then presented to the grinding surface in a manner well known to the art while the guiding member M is in its uppermost position, as shown in Fig. 1; The

guiding member M is then slowly moved downwardly,

The operator may utilize the notches 40 as a reference to insure that he has ground the drill-bit at the proper angle. By presenting the drill-bit into the corresponding notch, he can determine whether the proper angle has been given to the drill-bit during the grinding operation and whether the grinding has been performed symmetrically. If the cutting edges register along the bottom walls 41 of the corresponding aperture it) for the particular bit being ground and the spaces at the side are equal, the user may rest assured that the drill-bit has been sharpened properly.

In the use of the embodiment shown in Figs. 4 and 5,

the shaft 46 is supported solely by the electric drill 45.

The, user holds the electric drill in one hand. and inserts the drill-bit to be sharpened into the guide member 52 and presents the grinding surface with the aid of the magnifying glass in the same manner as described above with the embodiment shown in Figs. 1-3. It will be noted, however, that in this instance the guide member 52 is supported entirely and directly by the shaft 46 and that the sole support for the entire sharpening unit is provided by the drill 45 to which the attachment is connected.

The attachments described above have a number of distinct advantages. One of these advantages is that they are so very simple in construction and operation that.

even an inexperienced user may accomplish an eflicient grinding operation very simply, quickly and inexpensively. At the same time the grinding operation is an efficient one. Since the attachments are'constructed so simply they require a minimum amount of material and labor and hence their cost to the potential user is re-, duced to a minimum. As aresult, they can be manufactored and sold at a price range well within the means of the average household ownerwho desires to do at least a measure of such work himself.

In addition to the above, it will be noted that these attachments are readily portable and'can be constructed so as to'be quite small in size, thereby enabling the owner to' store them in small compass. Moreover, the

cost of the source of power which is normally attend- 7 ant with such a device has been eliminated for the owner can utilize his hand drill (which he already owns in order to accomplish the drilling operations) to provide the necessary source of rotary power. stantial saving is accomplished through the elimination of the need for a separate source of power to drive this simple attachment.

It should also be noted that the embodiment shown in Figs. 4 and 5 has an added advantage inthat no ad.- ditional structure is needed, not even a vise or special support to accomplishthe grinding operation. The attachment, when used in combination with the drill, is complete in itself and thus the cost of the pedestal or bench normally incurred with such instruments, is ob-;

viated.

It will, of course, be understood, that variousv changes may be made in the form, details, arrangement and proportions of the various parts without departing frorn'the scope of my invention.

What is claimed is: M

1. A portable drill bit sharpening assembly comprising a shaft, a grinding element mounted on the shaft for rotation therewith and having a grinding surface, a framework including a part encircling said shaft to turn thereon and the framework extending laterally of'the shaft, and a drill bit holding mechanism comprising a drill supporting and guiding member and a pivot coupling between the guiding member and the framework for turning on an axis always intersecting saidgrinding surfacesubstantially at the point of contact of the axis of the drill and always intersecting the axis of said shaft, and the guiding member being supported by the pivot coupling to maintain the line of contact between a supported drill bit and said grinding surface at thepoint of intersection of said pivot coupling turning axis and the grinding surface.

2. A portable drill bit sharpening assembly comprising a shaft, a grinding element mounted on the shaft for rotation therewith and having a grinding surface, a framework including a part encirclinglsaid shaft to turn thereon and the framework extending laterally of the shaft, and a drill bit holding mechanism comprising a drill supporting and guiding member and a pivot coupling between the guiding member and the framework for turning on an axis always intersecting said grinding surface substantially at the point of contact of the axis of the drill and always intersecting the axis of said shaft,

Thus a very suband the guiding member consisting of an elongate body of rigid material having a centrally disposed channel extending longitudinally thereof and having spaced laterally extending portions joined by the pivot coupling to the framework to maintain the line of contact between a drill bit supported in said channel and said grinding surface at the point of intersection of said pivot coupling turning axis and the grinding surface.

References Cited in the file of this patent UNITED STATES PATENTS Walker Feb. 20, 1900 Dickinson Sept. 27, 1921 FOREIGN PATENTS Great Britain 1900 Sweden Mar. 15, 1932 

